This is why I recommended Rebecca's mouth-stretching exercises in my January 25 blog post.
There are two common English sounds you need to really stretch into a smiley face for. One is the [æ] vowel, which is in "cat." The other is [l], especially and "l" sound at the END of a word.
These are two sounds you are going to struggle with. I provide corrective feedback in class, but the gist of it is that you have to move your mouth more when you speak English than when you speak Japanese.
Please speak English well!